Many UV light absorbers are known as ingredients for polymeric materials used to make ophthalmic lenses. UV absorbers are preferably covalently bound to the polymeric network of the lens material instead of simply physically entrapped in the material to prevent the absorber from migrating, phase separating or leaching out of the lens material. Such stability is particularly important for implantable ophthalmic lenses where the leaching of the UV absorber may present both toxicological issues and lead to the loss of UV blocking activity in the implant.
Numerous copolymerizable benzatriazole, benzophenone and triazine UV absorbers are known. Many of these UV absorbers contain conventional olefinic polymerizable groups, such as methacrylate, acrylate, methacrylamide, acrylamide or styrene groups. Copolymerization with other ingredients in the lens materials, typically with a radical initiator, incorporates the UV absorbers into the resulting polymer chain. Incorporation of additional functional groups on a UV absorber may influence one or more of the UV absorber's UV absorbing properties, solubility or reactivity. If the UV absorber does not have sufficient solubility in the remainder of the ophthalmic lens material ingredients or polymeric lens material, the UV absorber may coalesce into domains that could interact with light and result in decreased optical clarity of the lens.
Examples of polymeric ophthalmic lens materials that incorporate UV absorbers can be found in U.S. Pat. Nos. 5,290,892; 5,331,073 and 5,693,095.
In addition to blocking UV light, some ophthalmic lenses also block blue light. See, for example, U.S. Pat. Nos. 5,470,932 and 5,543,504. These lenses block both types of light by using two chromophores: a UV absorber and a yellow dye.
There is a need for UV absorbers that are capable of blocking not only UV light (400 nm and below) but also blocking at least some light in the 400-450 nm range.